1. Field of the Invention
The present invention relates to a method and an apparatus for producing ceramic green sheets, the method and apparatus being used for producing ceramic green sheets for use in laminated capacitors and other devices, and more particularly, to a method and an apparatus for producing ceramic green sheets each supported by carrier films.
2. Description of the Related Art
In recent years, in laminated ceramic electronic components such as laminated capacitors, the thickness of ceramic layers disposed between internal electrodes is becoming very small. This results in the reduced thickness of ceramic green sheets used. Therefore, typically, a ceramic green sheet is formed on a carrier film constituted of a synthetic resin film, and is treated while being supported by the carrier film.
When forming a ceramic green sheet by applying ceramic slurry on a carrier film, the carrier film must be kept clean. Thus, various methods have been adopted in order to remove the foreign substances, such as dust or dirt, on the surface of the carrier film.
FIG. 7 is a schematic side view for explaining a first conventional method for removing the foreign substances on a carrier film. Herein, a carrier film 51 is transferring in the direction of the arrow A shown in the figure, that is, in the longitudinal direction of the carrier film 51. An adhesive roll 52 is in contact with one surface 51a of the carrier film 51 in the course of transfer, and the foreign substances on the one surface 51a of the carrier film 51 are removed by the adhesive force of the surface of the adhesive roll 52.
On the other hand, FIG. 8 is a side view for explaining a second conventional method for removing the foreign substances on a carrier film. Herein, a carrier film 53 is transferring in the direction of the arrow A shown in the figure. In order to remove the foreign substances on the one surface 53a of the carrier film 53, a suction nozzle 54 is disposed at a position adjacent to the surface 53a. The foreign substances on the one surface 53a of the carrier film 53 are sucked and removed by the suction force of the suction nozzle 54.
When using a foreign substance removal mechanism such as the adhesive roll 52 shown in FIG. 7 or the suction nozzle 54 shown in FIG. 8, the path line of the carrier film 51 or 53 in the course of transfer is not stabilized. This causes fluctuations of the transfer speed and tension, which results in local variations in the thickness of a ceramic green sheet.
That is, each of the carrier films 51 and 53 in the course of transfer is in an unstable state. Therefore, for example, in the method shown in FIG. 7, due to variations in the adhesive force of the adhesive roll 52, the carrier film 51 fluctuates in the direction of the arrow B shown in the figure, that is, in the thickness direction, and hence, the path line of the carrier film 51 is not stabilized. Consequently, when ceramic slurry is applied after the removal of foreign substances, variations in the amount of ceramic slurry applied occur, and the ceramic green sheet ultimately obtained is inevitably subjected to variations in the thickness thereof.
Likewise, in the method shown in FIG. 8, the path line of the carrier film 53 is not stable because of variations in the suction force of the suction nozzle 54, and the ceramic green sheet obtained also inevitably undergoes variations in the thickness.
In particular, when the thickness of the ceramic green sheet is reduced, the influences of fluctuations of the path line of the carrier films 51 and 53 become more significant, and thus, variations in the local thickness of the ceramic green sheets have constituted a more serious problem.
In order to overcome the problems described above, preferred embodiments of the present invention provide a method and an apparatus for producing ceramic green sheets, the method and apparatus preventing fluctuations of the path line due to a foreign substance removal device, without reducing the dust removing effect, and allowing ceramic green sheets having minimal variation in the thickness thereof to be thereby stably produced.
In accordance with a preferred embodiment of the present invention, there is provided a method for producing ceramic green sheets. The method preferably includes the steps of transferring a carrier film in the longitudinal direction thereof, removing foreign substances on the carrier film surface opposite to the carrier film surface in contact with a support roll, at the portion where the carrier film is in contact with the outer peripheral surface of the support roll, using a foreign substance removal device, while supporting the carrier film by the support roll so that the transfer direction of the carrier film is changed by the support roll, and forming a ceramic green sheet by providing ceramic slurry on at least one surface of the carrier film after the foreign substances have been removed.
Preferably, the portion where the foreign substances are removed by the foreign substance removal device is located approximately at the longitudinal center of the carrier film portion where the carrier film is in contact with the outer peripheral surface of the support roll.
In a particular aspect of the method in accordance with a preferred embodiment of the present invention, the ceramic slurry is applied on the carrier film surface from which the foreign substances have been removed.
In another particular aspect of the method in accordance with a preferred embodiment of the present invention, the ceramic slurry is applied on the carrier film surface opposite to the carrier film surface from which the foreign substances have been removed.
In accordance with another preferred embodiment of the present invention, there is provided an apparatus for producing ceramic green sheets. The apparatus includes a delivery roll for feeding a long carrier film, a transfer unit arranged to transfer the carrier film drawn out from the delivery roll in the longitudinal direction thereof, a support roll supporting the carrier film on the outer peripheral surface thereof so as to change the transfer direction of the carrier film, a foreign substance removal device disposed so as to remove the foreign substances on the carrier film surface opposite to the carrier film surface in contact with the support roll, at the portion where the carrier film is supported on the outer peripheral surface of the support roll, and a ceramic-slurry applying device for applying ceramic slurry on one carrier film surface from which the foreign substances have been removed, and for thereby forming a ceramic green sheet.
Preferably, the foreign substance removal device is disposed so as to remove the foreign substances on one carrier film surface approximately at the longitudinal center of the carrier film portion where the carrier film is contact with the support roll.
In a particular aspect of the apparatus in accordance with a preferred embodiment of the present invention, the foreign substance removal device is a contact-type foreign substance removal device for removing the foreign substances while being in contact with one surface of the carrier film.
In another particular aspect of the apparatus for producing ceramic green sheets in accordance with a preferred embodiment of the present invention, the foreign substance removal device is a noncontact-type foreign substance removal device for removing the foreign substances on one carrier film surface without contacting the carrier film supported by the support roll.
In still another particular aspect of the apparatus for producing ceramic green sheets in accordance with a preferred embodiment of the present invention, the support roll is a drive roll coupled with a rotational driving source, and the drive roll doubles as a least one portion of the transfer unit.
In a further particular aspect of the apparatus for producing ceramic green sheets in accordance with a preferred embodiment of the present invention, the ceramic-slurry applying device is disposed so as to apply the ceramic slurry on the carrier film surface from which the foreign substances have been removed.
In a yet further particular aspect of the apparatus for producing ceramic green sheets in accordance with a preferred embodiment of the present invention, the ceramic-slurry applying device is disposed so as to apply the ceramic slurry on the carrier film surface opposite to the carrier film surface from which the foreign substances have been removed.